Creating a graph on the surface of an object
You may do it using a curve and then convert it to mesh.


Add a curve, scale it to make it longer and then subdivide many times with W (set the segments number in a Tool Shelf). Form its shape as you like (to be accurate use background image as a reference).


Select all points with A, then press V-->Vector to change the handle type. Add bezier circle and do the same with it. Rotate it 45 degrees (you may change the circle's shape as you like though).


Select the curve and go to the Curve header, set it's type to 2D. Set the bezier circle as a Bevel Object target. Check the Fill Caps checkbox in a Geometry panel. Scale the bezier circle to adjust the curve's thickness. Finally press Alt+C-->Convert to Mesh in Object Mode.


Enable Auto Smooth checkbox in the Normals panel of the Mesh Data header to make the object smooth.


Use a snapping tool to attach the curved mesh to your robot. Click the magnet icon and change the snap element type to Face.